This invention relates to a container, engagement ring and cover assembly which is constructed incorporating either one or both of two basic novel concepts, either of which particularly adapt the assembly for preferably being molded totally of plastic. According to the one novel concept, an inverted U-shaped portion of the engagement ring telescopes over an open upper end of the container sidewall with transverse interengagement between flanges thereof, and an edge portion of the cover overlies and extends downwardly into a U-shaped inward extension of the engagement ring with transverse interengagement between flanges thereof. In the other novel concept, an inverted U-shaped portion of the engagement ring telescopes an upper open end of the container sidewall positioning an engagement ring generally vertical wall outwardly abutting an inner side of the container sidewall and a generally vertical wall on the cover edge portion is positioned outwardly abutting the engagement ring wall, with the engagement ring and cover being constructed and arranged to exert an outward transverse pressure for pressure sealing between the cover and engagement ring walls and between the engagement ring wall and the container sidewall inner side.
Various forms of prior container constructions have been hereinbefore provided involving a container, engagement ring and cover assembly. Most of these particular prior constructions have been formed totally of metal, such as the usual tinplate. For instance, one of the prime examples is the common metal paint can in which paint and similar materials are commonly marketed and used.
With the usual paint can, the container thereof is usually formed with a cylindrical sidewall having a bottom wall secured thereto by means of the usual multiple-folded seam commonly used in metal containers and cans. An engagement ring is similarly multiple-fold seam secured to the upper open end of the container sidewall, the engagement ring extending transversely inwardly from the sidewall and being formed with a somewhat V-shaped annular recess spaced inwardly from the container sidewall and extending around the same. The cover has the edge portion thereof formed with a reduced size, somewhat matching V-shaped recess proportioned such that the cover edge portion recess may be press-fit forced downwardly into the engagement ring recess for thereby pressure sealing the contents of the container. Furthermore, a transversely projecting flange is formed at the periphery of the cover exposed for engagement by a tool to selectively remove the cover from its press-fit retention by the engagement ring so that container contents may be used with the cover being capable of being returned to its assembled positioning and press-fit retainment due to the metal rigidity.
Beyond the foregoing purely functional pressure sealing and containment features of the prior paint cans and similar containers, such containers are required to have certain other particulars of construction necessary for proper factory conveying and ultimate marketing. One of these is that the container sidewall must be vertically straight throughout between the upper and lower end portions thereof. One of the principal reasons for this requirement is so that labeling may be conveniently applied thereto, whether by direct printing thereon or by adhesively applied labels. If the container sidewall is other than straight, obvious difficulties are presented.
Another requirement for convenience in conveying of the containers in the manufacturing facilities during filling, closing, packing and storage, and also associated with the straight container sidewall requirement, is that the upper and lower end portions at the sidewall of the container must project transversely equal distances. In other words, once the engagement ring has been assembled with the container and both before and after the assembly of the cover, the center axis of the container must be parallel to the surface upon which it rests when the container is laying on its side. This is necessary so that the container may be conveyed by rolling the same on its side during which it must roll in a straight line.
As hereinbefore stated, most of the prior paint cans and similar containers incorporating container, engagement ring and cover assembly have been formed of metal and it has now been determined that if this type of container could be constructed so that it is adaptable to being totally molded from plastic, quite extensive cost savings and other benefits could be appreciated in the manufacturing industries making use of this type of container. However, in order to satisfactorily accomplish such conversion from total metal to total plastic, the semi-assembled and finally assembled plastic container would have to meet the exact same requirements as met by the prior metal container. To meet all of these requirements with a molded plastic container presents a multiplicity of problems which require solutions. Also, still other problems are presented purely from the standpoint of plastic molding procedures which are not present in the entirely different metal forming procedures.
Comparing the structure of the metal container of the type herein involved and the resultant molded plastic container if such conversion is made, the metal container has the bottom wall thereof multiple-fold seam connected to the lower end of the container sidewall and the engagement ring similarly seam connected to the upper end of the container sidewall. Obviously, the common multiple-fold seam used with metal containers cannot be used in a plastic container. Although with a plastic container the connection of the bottom wall with the container sidewall is not a problem since it can merely be integrally molded therewith, it does become a problem as to just how to provide a connection between the upper end of the container sidewall and the engagement ring, particularly keeping in mind that it must be a pressure sealed connection.
Furthermore, with the metal container, the engagement ring and cover are merely formed with mating V-shaped annular recesses or grooves and the cover is friction retained with the engagement ring merely by a friction fit between the mating V-shaped portions. It is again apparent that with plastic, friction retention will not suffice. Physical interengagement between the plastic cover and engagement ring must be somehow incorporated. In addition with the plastic, a second pressure sealing zone must be provided to complete the pressure sealing requirements.
Still further, one of the requirements of the metal container is that it have a vertically straight sidewall for the various reasons enumerated and this requirement presents a major difficulty in normal plastic molding processes. Most prior molded plastic containers, regardless of the other particular structure thereof, have had tapered sidewalls. The principal reason that the sidewalls are tapered is so that the container after molding can be easily removed from the mold. Here, however, we must have a straight sidewall between the sidewall end portion connections to the container bottom wall and to the upper engagement ring assembled therewith.
Furthermore, the end portion connections of the container sidewall to the container bottom wall and to the assembled engagement ring must protrude transversely equal distances so that the assembled container, whether assembled merely with the engagement ring or with both the engagement ring and cover, will roll in a straight line for the reasons hereinbefore discussed. This, therefore, again also involves the pressure sealing connection between the upper end portion of the container sidewall and the engagement ring assembled therewith so that the transverse protrusion of the assembly properly satisfies the equal distance requirement.